FIG. 1 shows a schematic diagram of a structure of a pixel driving circuit of a basic Active-matrix organic light emitting diode (AMOLED) display device in the prior art. The driving circuit has a 2T1C structure, wherein T1 is a switching transistor, T2 is a drive transistor, Cst is a storage capacitor, and OLED is an organic light emitting diode. When a scanning line G outputs a scanning signal and the transistor T1 is turned off, a grayscale data signal Vdata charges the storage capacitor Cst via T1. When the storage capacitor Cst is charged to a predetermined value, the transistor T2 is turned on, and a driving signal ELVDD lightens the OLED via T2.
After an AMOLED display device is turned off, a natural discharge process of the data voltage Vdata output by a source driving chip is slow, which affects a discharging speed of point A. Moreover, when the display device is turned off, a continuous and effective turn-on voltage cannot be ensured by a scanning driving chip, which causes that T1 is turned off before the data voltage Vdata at point A discharges completely. As a result, a discharge path for the voltage at point A is blocked, and thus a discharge process at point A is adversely affected. Therefore, after the display device is turned off, an afterimage is generated.